Planting corn, soybeans and certain other crops with limited soil preparation has many advantages, including reduced soil erosion, less runoff, fuel conservation, and less time required for planting. Sloping soils which would sustain too much erosion if planted to row crops by conventional methods can be safely planted using limited tillage only.
Planting systems in which very minimal tillage is done to permit placement of seed in the soil have usually been termed "no-till" planting. It is a misnomer, since obviously some tillage must be done to make an opening in the soil to receive the seed. Systems which do more than the very minimal amount of tillage to make an opening for the seed, but less than plowing, and limit tillage more or less to the immediate row zone, are called by various names such as "minimum tillage," "reduced tillage," "rip-plant," etc. These intermediate tillage-planting systems retain many of the advantages of "no-till" planting, but are a concession to the fact that something more than merely making a minimal opening in the soil to receive the seed is desirable in order to provide a more optimal environment for seed germination and seedling emergence, particularly in soils which tend to be hard, cloddy, sticky or crusty. Loose, friable, granular and flowable soil is needed, at least in the immediate row zone, to permit reliable placement and coverage of the seed by the planter, and to help ensure that good soil-seed contact is established by the firming device of the planter. Good contact is essential so that moisture transfer from soil to seed can be initiated and continue until plant roots emerge to take over the moisture acquisition function.
"No-till" planting units frequently have a flat, ripple, or fluted coulter which goes directly in front of the planter opener, cutting through surface trash and slicing two to four inches into the soil. The seed-furrow opening device on the planter, often of the double-disc type, follows directly in the slot or impression made by the leading coulter and deposits seed to a preset depth. A press wheel on the planter then squeezes the slot closed by exerting pressure on either side of, or directly over the seed, or both. This system works well in mellow or low-strength soils under a wide range of moisture levels, and is satisfactory in high-strength, crusting soils when moisture levels are optimal.
In clays or other soils which tend to be sticky when wet, and hard or brittle when dry, the "no-till" planter may penetrate under dry conditions only with the addition of much static weight, if at all. If penetration is accomplished, the seed covering and soil firming components of the planter may not function properly because the soil has not been rendered loose and flowable by the "no-till" coulter and seed furrow opener. Many of these same soils tend to be sticky when slightly wet, and although penetration can then be easily accomplished, the plasticity of the soil makes good seed coverage difficult and unreliable. These soils which are more difficult to handle satisfactorily with "no-till" planters tend to occur predominantly on slopes where the limited tillage approach to row-crop production is most needed.
In an attempt to overcome the penetration problem, "no-till" planting units have been modified by placing chisel points, subsoilers and other tillage elements directly behind the leading coulter and in front of or in lieu of the seed furrow opener of the planter. These elements aggressively penetrate even hard, dry clay soils without the addition of weight; in fact, they must usually be supported by gauge wheels, tractor lift or both to prevent soil reaction forces from pushing them too deep. Some units have included tines, fluted coulters or other elements behind the chisel shank to fill voids in the slot and firm the soil ahead of the planter seed furrow opener. This approach has been successful with mellow soils because the lifting action of the chisel or subsoiler point causes these mellow soils to crumble and flow, creating a loose, soft, friable and highly desirable seedbed.
However, this approach has not proven successful with other than mellow soils because when dry, crusted soil is lifted by a chisel or subsoiler point, it often breaks along natural fracture lines into large clods which are unsuitable for a seedbed. These clods tend to be rolled or pushed partly out of the row zone, leaving an obstacle-strewn furrow with little or no loose soil available for seed coverage. The planter is tossed and jolted as it negotiates the obstacle course, causing poor seed plate cell fill, inconsistent seed furrow opener penetration, and unreliable seed coverage. Packer or filler tines, coulters, or wheels behind the chisel shank do not adequately crush, slice or otherwise disintegrate clods to create a satisfactory seedbed because (1) the clods are unrestrained and can move to avoid these elements; (2) not enough force can be brought to bear to crush them; or (3) loosened soil beneath the clods may yield and prevent the development of enough pressure to crush clods.
With the foregoing in mind, it is an object of the present invention to provide an improved soil conditioning device for minimum tillage planting which is particularly useful in clay-type soil but which functions equally well in other soils and which overcomes the deficiencies of prior limited tillage planting devices and produces a narrow row zone of loose, soft and friable soil.
A more specific object of the present invention is to provide a minimum tillage planting apparatus with improved soil conditioning means which provides loose, soft and friable soil for receipt of seeds even in clay-type soil.